And caleb



N. PETERS, FHOTO-LITHOGRAPHEH, WASHINGTON, D C.

i To allwhom timfz/ concern;

constitutes a tlieqsanie.`

' 1 '.Il '11i i .i Trios. w. PRATT. or `uonwiori, connncricunnnn cALEB i cHUsETTs.

- ma@ man cinica rna'rfr, or sesion. Massa! @semanas oa f seeifiaami f nttiffratat No. 3,523, eared Apri 4, .1844.5

`lBe. it known that we, THOMASV V. Pnii'r'i, of Norwich,i `e.Stateo'Connecticuu `and Canne Pnn'rr, oston, -in the [Statevot Massachusettgl. e vented" a new or proved. mode .i or. nstructing truss-frames for `bridges ,andsuchfllotherarchitectural structuresor purposes to, which the same` maybe successfully" applicable, andfhthat the followingfgz'specicatio-n h thereof, ,talren in `connection with `accompanying drawings, `full and exact `description of Insiaid specificationfwe hayeset `drth the ...nature and principlesl of x our y. improve!` nient `by which it,l `may be distinguished from others .of `like character" together with. .such parts of the` sametasweclaim as our discovery and believetobe new.

Of `the drawings ab ve mentioned Figure 1, exhibits a side elevation truss constructed according to the principles to be hereinafter defined." .Fig. `2, represents a top view thereof, or aview of the upperside of the upper stringtimbers of the saine. Fig.` 3, is a plan of the bottoniofsaidtrussor the lower side of the lower string timbers. Fig. 4, is a horizontal section exhibiting theupper face ot.` the lower Stringer. While Fig;` 5 is a transverse vertical section of the whole truss, taken at or near the middle thereof.

Fig. 6 exhibits a modification of the truss, wherein the upper Stringer is crowned or arched. h

A, Figs. l, 3, 4, 5, represents theinferior or lower Stringer which may be composed of any numberofplanks or timbers a, a, a,

arranged side by side, and spliced and bolted `toget-her in any convenient manner, or

the saine may be otherwise suitably constructed. Upon this Stringer `a series of vertical posts B," B, B, B, is elevated, the same resting upon shoes 7), ZJ, interposed beztween their eetand `the upper surface of `the stringer as seen in the drawings. These shoes may be` formed of pieces of hardwood or `planks orotherproper material, extending laterally across the Stringer and let or `notched down a short distance into the same in order to securethein in their respective positions. `The footcof `each post may also be stepped a short distance into the shoe, if desirable, `and upon each shoe two or more posts may `be disposed las `seen. in Fig. 5. Other` andsimilar" shoes or cap i piecesc, are placedon'the top `the i posts, andreceive upon their upper surfaces the superior `or upper Stringer C, which is constructed inwall respects like the lower stringer," before mentioned and extends e parallel with the same or from post to post as exhibited in FigQly or the salidupper` Stringer may be curved longitudinally as seen in FiggG.` series ot'transverse bear- V or `straliniing blocks d, d, d, `suitablyT formed `from hard `wood Vor metal, extends beneath the `lower Stringer andposts, `the samebeinglet into the lower `face of the Stringer and situated )directly under the posts,as seen inFigs. fl, 3. `Another series e,"`e`,;e, of such blocks is similarly arranged upon the upper face of` the superior Stringer C as seen in the drawings." Main braces i D,"D, D&c`., and counter braces E, E, E,

"crossing each other diagonally as seen in Fig.` l, extend from and through the lower theupper blockse, c, ofthe upper Stringer,

blocks "d, d, under the` posts to and through each brace being a -metallicqrod orlibar,

which has a suitable head f, formed upon its upper end, `and `a screw and nuto arrangeduupon `its lower end, sothat when; the nut `is turned in the right direction upon the screw; it bears upon one of the beveledV faces of the lower block, or a suitable washer placed `onthe face of the block and draws the head of the brace" firmly against the opposite beveled face of thesupper h block.

y counter brace, ofeach of which there may be The `tension braces maybe placed `on the sides of the truss if desirable, or they any number passing from the lower to the upper blocks of the said panel according to the strength requisite in the truss. Should it ata-ny time be desirable to in-` crease the strength of the trussa beam F, of suit-able length, may be arranged centrally and directly under and in contact with the upper stringer, as seen in Figs.. l, 5, and from each extremity of this beam, an inclined beam G` may Aextend to the lower stringer, into or upon which it may be stepped in any convenient manner, the said central and side timbers forming what may be termed an arch beam; or instead of the said method of constructing an arch-beam it may be arranged in connection with the upper and lower stringers or in connection with the upper stringer and the abutments of the bridge or truss in any of the methods usually known and practiced in carpentry.

ln some situations where a truss may be employed which has its braces and counterbraces arranged'as exhibited in Fig. l, the lower Stringer may not be requisite as the flooring or whatever is to be upheld by the truss may be' depended directly from the lower straining blocks or otherconvenient parts, the former of which in such case will generally be arranged in direct Contact with the feet of the posts.

The several iron braces are subjected to a tension strain and being arranged as herei'nbefore described, they draw .or conine the posts and st-ringers together. More or less camber may be easily given to the truss by means of the nuts upon the screws of the braces, which on being turned in the requisite direction, lengthen or shorten the distances between the heads and nuts of the braces to such Adegrees as may be requisite to produce the necessary camber. In the truss represented in Fig. l, the braces of each panel, being coupled by means of the straining block, with the counter braces of the succeeding panel, Vand the counter braces also of the same, being in a similar manner cou pled with the braces of the succeeding panel, a connected strain is thus kept on the tension braces, independent of the other'parts of the frame, whereby the tie beam or lower Stringer is more or less relieved of a portion of its st-rain, according to the disposition of the weights producing the said strain. The bracing by means of tension bars extending diagonally across each. panel of a bridge truss has been long known and used; but the system of bracing and counterbracing, by means of tension bars crossing each other in each panel, is believed to be new, and not only affords the lmeans of regulating the general camber of a bridge, but allows it to be drawn up, or depressed, in any particular segment, at pleasure, andv thus furnishes a means of regulation not derivable from the single tension braces in each panel.

Having thus explained the nature of our invention we shall claim-V A The above described method of constructing a truss, that is' to say the combination 'of two diagonal tension braces and straining p blocks, in each panel of the truss frame of a bridge; by means of which the camber may be regulated so as to increase vor to diminish it, either in whole or in sectional part of the bridge, the whole beingv constructed and operating, substantially .as herein before set forth.

In testimony that the foregoing isa true Ti-ioMAs w. PRATT. cALEB PRATT.

lVitnesses:

R. H. EDDY, v EZRA LINCOLN, J r. 

